[(Yet Another) FLH Upper Bass Build]

On 4/6/2019 at 7:24 PM, ClaudeJ1 said:

IMHO, I would target 80 Hz. as the cutoff for your Straight Axis Midbass. I have been involved in building 7 SPUD Tapped Horns, and the lower the Xover point, the better. Just sayin'. You might want to try JC's horn with a single 12" driver instead of 2 for 1/2 the height.

Hi @ClaudeJ1, I strongly agree that tapped horns sound better the lower the crossover.  I can hear the nastiness coming from the upper-end.  I don't think it makes TH's a "bad speaker", simply that they need to be implemented intelligently and within their performance envelope.  

 

Sadly, 80 Hz is a difficult target to hit (for me), while also satisfying my physical size limits and upper X-over plans (~ 400 - 500 Hz).

[(Yet Another) FLH Upper Bass Build]

Gents -

 

First, regrets for a long-delayed reply.  It's simply been super-busy around here lately, and there's never enough quiet time to focus on horns after satisfying other time commitments.

 

Second, a HUGE THANK YOU to JWC and Seti for your support.  JWC's dual driver horns were the inspiration for this project, mostly for his results, but even more for a logical, well-documented thought-process.

 

Third, I moved the thread to a different forum, assuming (rightly or wrongly) my DIY project might be a distraction in this Klipsch-centric forum.

 

For those interested in following, here you go:  

 

https://www.diyaudio.com/forums/multi-way/336290-upper-bass-tractrix-flh.html#post5779878

 

[(Yet Another) FLH Upper Bass Build]

Thanks, Moray.  I've communicated with John in the past.  I need to pay him a visit sometime!

[(Yet Another) FLH Upper Bass Build]

Hi,

 

This is my first post, although I've been a long-time follower and longer-time Klipsch user.  

 

A bit about myself:  I've been listening to horns for awhile. My first "high-end" system was Klipsch Heresy powered by Counterpoint tubes and sourced with vinyl (back in the day).  I took a detour with non-horn loudspeakers for a few years, but returned to horns with Dr. Edgar's Edgarhorns, and now listen to a multi-way horn system of my design.  

 

I'm moving forward on a dual-driver, tractrix FLH upper-bass horn, with these design goals (but I'm still uncertain if all are achievable):

 

1) FLH architecture for a clear upper end

2) BW: 100 - 600 Hz (2.5 octaves)

3) Directivity:  90 degree BW at 500 Hz minimum, and as high as possible

4) SQ focus on transition from upper-bass to midrange, rather than ultimate low-frequency extension due to:

     - Human hearing is more sensitive in the midrange than low-frequency

     - Deliver dynamic, visceral "thwack" over upper-bass extension

5) Tractrix curve - to integrate well with the midrange

6) Crossover ~ 500 Hz to 1) Edgar 350 Hz round tractrix / B&C DCM50, and later to 2) K-402

7) Crossover ~ 90 Hz to stereo Danley SPUDs

😎 Mouth of sufficient size to minimize ripple

9) Length balanced for extension and minimal group delay

 

Assumptions:

 

- Half-space

- Quarter-sized

- Dual drivers to minimize horn length and driver excursion

- Fits through doorways (~ 31" max)

 

One source of inspiration for me has been @jwc bass horn projects.  I find his projects well-considered and clearly articulated.  Also, @setifor documenting so much of interest to horn-lovers like me.  Thanks, @jwc and @seti!

 

First, I selected B&C 10" 10MD26 woofers because I have some familiarity with them from past builds.  They are very sensitive, with lightweight paper cones, and strong motors.  I chose 10" drivers (rather than 12" or 15") to integrate with the midrange.

 

https://www.bcspeakers.com/en/products/lf-driver/10-0/8/10md26

 

Using Edgar's and PWK / Delgado AES papers as a guide, the following parameters are calculated:

 

MASS ROLL-OFF

 

Fhm = 2 * Fs / Qes

 

        = 2 * 76 / 0.22

 

        = 724 Hz

 

THROAT AREA

 

St = ( 2 * Pi * Fs * Qes * Vas ) / c

 

    = ( 2 * Pi * 76 * 0.22 * 0.20 ) / 343

 

    = 58.47 cm^2

 

BACK CHAMBER VOLUME

 

Vb = Vas / [ ( Fc / Fs * QEs ) ] -1

 

     = 20 / [ 90 / ( 76 * 0.22 ) - 1 ]

 

     = 4.3 L

 

REACTANCE ANNULLING CHECK

 

Fc = Qes * Fs * ( 1 + Vas / Vb )

 

     = 0.22 * 76 * ( 1 + 20 / 4.3)

 

    = 90.19 Hz

 

Finally, to the reason for my post....!

 

My experience is mostly running Hornresp.  Since I need data in AutoCAD compatible format for the build (as well as curiosity about cross-checking David's Hornresp with Edgar's / Keele's maths) I chose to model on Volvotreter's excel tool download.  I'm running into an obstacle though, because I haven't figured out how to model a dual driver design on Volvotreter's tractrix calculator.  

 

***Can anyone share guidance on this?

 

Also, Hornresp uses a forcing function to calculate horn length, given inputs of throat area, mouth area, and Fc.  But the result seems to differ from Volvotreter's worksheet.  Usually, Hornresp results in a longer path length.  Naturally, I want to minimize bulk while still attaining my design goals.

 

I think JWC's full-sized horn was 61 cm deep.  So perhaps I'm guilty of operator error because I get a differing path length when I model his horn on Volvotreter's tool.

 

In any case, I suspect I'm making a simple mistake and am here seeking a little oversight and adult hand-holding.

 

Thanks for any clarification.  Cheers!